What is Concrete Formworks (Shutterings)?
Concrete formworks (shutterings) are used for casting fresh concrete in structural members such as walls, slabs, beams, columns, footings, etc. They act as a temporary mould to provide support to the concrete while it sets. This helps the structural member to gain the required strength to bear its self-load and other loads from other members.
Types of Structural Formworks or Shutterings
Formwork or shuttering is available in various materials, usage and types of structural members. Different types of formworks are used for different structural members based on the need and requirement. However, their core functioning remains the same, which is to provide support to the concrete while it sets.
Types of Formwork (Shuttering) Based on Structural Member:
Formworks are used in construction of reinforced concrete foundations, columns, slabs, walls etc., and these are named as follows:
- Footing Forms – Formworks for foundation
- Column Forms – Formwork for RCC Column construction
- Wall Forms – Formwork for RCC wall construction
- Floor Forms – Formwork for construction of RCC Slabs
Footing Forms – Formworks for Foundation
Footing forms are formworks used for the construction of foundations for columns and walls. They come in a variety of shapes and sizes, depending on the type and dimension of the footing.
Types of Footing Forms: Depending on the type of structural member, there are various types of footing forms including rectangular footing forms, square footing forms, and circular footing forms. Each type of footing form has its own set of advantages, helping to ensure that the foundation is stable and secure.
Benefits of Footing Forms: Using footing forms during the construction process can provide numerous benefits, including ease of installation, cost savings, and improved structural integrity. Additionally, the use of formworks can help to reduce labor costs, as they can be quickly and easily installed.
Advantages of Using Footing Forms: Footing forms provide many advantages when used during the construction of foundations. They are easy to install, cost effective, and help to ensure structural integrity. Additionally, using formworks can reduce labor costs and improve the efficiency of the construction process.
Components of Footing Forms:
Column Forms – Formwork for Concrete Column Construction
Reinforced concrete columns are subject to lateral pressure due to their small cross-section, high heights, and rapid concrete placement. To ensure the formwork stays secure, tight joints and strong ties must be provided. As the size of the concrete column increases, the stiffness of the formwork must be increased. This can be achieved by using thicker sheathing or adding vertical stiffeners to prevent sheathing deflection.
Wall Forms – Formwork for RCC Wall Construction
Formwork for Wall Construction: Formwork is used to create a concrete wall structure, and the pressure exerted on it is usually lower than that of columns. The components of formwork for wall construction include panel sheathing, studs, braces, ties and spreaders.
Panel Sheathing: Panel sheathing is used to form the wall shape and keep the concrete in place until it sets. It is a key component of formwork for wall construction.
Studs: Studs are used to support the sheathing and Wales, forming a frame that keeps the forms aligned and the studs in place.
Braces: Braces are used to prevent deflection of the forms when under lateral pressure, and to keep the formwork upright.
Ties and Spreaders: Ties and spreaders are used to ensure that the sides of the forms are kept at the correct spacing. They are essential for maintaining the integrity of the formwork.
Floor Forms – Formwork for construction of RCC Slabs
Positioning of the Girder or Beam Form:
The first step of a formwork assembly for reinforced concrete slabs is the positioning of the girder or beam form at the bottom. The girder side forms overlap the bottom form and rest on the shore heads and the sides of the column form. To keep the formwork in place, ledger strips are nailed to the shore heads with double-headed nails. Additionally, larger girders should have the side forms vertically stiffened to prevent buckling.
Strike-Off Formwork:
When constructing the girder and beam forms, each part must be removed without disturbing the remainder of the form. Strike-off formwork begins with the beam and girder sides, followed by the column forms, and finally by the beam and gird bottoms.
Slab-on-Grade Forms:
Slab-on-Grade forms are formworks designed for concrete slabs placed directly on the ground. These forms are typically quite basic, as concrete is placed on a leveled and compacted base, such as earth or gravel, which does not require additional support.
Slab-on-Grade Formwork assembly is carried out as follows:
Preparation of Slab-on-Grade Formwork: Plank, plywood, or steel forms are used for forming and supporting the open edges of concrete. These forms are held in place by supporting with wooden pegs.
Placement of Reinforcement: The reinforcement in slab (if specified in the structural drawing) should be placed on its proper location according to the drawing on chairs, bolsters, and spacers made of either metal or concrete.
Construction of Joints: If the slab is to be casted in sections, construction joints must be provided between them, which will transmit shear from one to the other. The details of construction joints should be followed as per structural drawing.